Serious bacterial infectious diseases are diseases characterized by expressing serious bacterial infections such as pneumonia, infective endocarditis, osteomyelitis, osteoarthritis, meningitis, sepsis, and the like among infectious diseases caused by bacteria, and their incidence rates have increased rapidly with an increase in a group of target patients caused by recent population aging and the spread of multidrug resistant bacteria caused by the indiscriminate use of antibiotics. The multidrug resistant bacteria causing serious bacterial infectious diseases include Enterococcus spp., Staphylococcus aureus, Klebsiella pneumonia, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. as known in the art.
It was reported that serious infections caused by multidrug resistant bacteria generally appear in the form of nosocomial infection, and the mortality rates caused by the serious infections are high, that is, the mortality rates are 5.4% and 29% in the case of pneumonia and sepsis, respectively. Also, a recent survey shows that patients should stay in the hospital for a long time when the patients catch serious bacterial infection, the return on investment spent for treatment is low, and the yearly cost of illness caused by the infection with multidrug resistant bacteria account for at least 1 trillion won in Korea. Moreover, the recent emergence of the multidrug-resistant bacteria in the local communities as well as the nosocomial infections caused by the multidrug resistant bacteria have been reported, and thus is expected to become a big issue on the national health service in the future.
In this regard, methods used to diagnose serious bacterial infectious diseases include biochemical methods, such as a method of identifying bacteria by performing in vitro bacterial cultures on clinical samples such as blood. However, the aforementioned methods based on the analysis results of bacterial genomics (metagenomics) has drawbacks in that it is possible to identify only 1% of the entire bacteria, and a period of at least 5 days is required to perform a bacterial culture. So far, antibiotics have been used based on the clinical experiences without having no information on bacteria.
Meanwhile, it was reported that prokaryotic cells such as bacterial cells and eukaryotic cells such as host cells (for example, human cells) secrete vesicles into the extracellular space, and the secreted vesicles perform various functions. Extracellular vesicles secreted by the bacteria contain endotoxins (lipopolysaccharides; LPS) and bacteria-derived proteins and genes and have a size of 20 to 100 nm, and thus are generally referred to as nanovesicles. It was reported that extracellular vesicles are found in a variety of human or animal secretions, excretion or tissue washes, and it was known that the extracellular vesicles present in tissues reflect the state of tissues secreting the vesicles. Also, it was reported that the extracellular vesicles can be used to diagnose diseases.
However, there is no research conducted on methods for identifying bacteria causing a serious bacterial infection through analysis of genes in bacteria-derived nanovesicles present in the human body and predicting resistance of such bacteria to antibiotics.